Modified atmosphere packaging generally refers to the practice of modifying the composition of the internal atmosphere or headspace of a package in order to improve the shelf-life of the product. The product is typically a food product but may also include pharmaceuticals or other types of products. The modification usually involves attempts to lower the amount of oxygen in order to slow down the growth of aerobic organisms and the speed of oxidation reactions. The removed oxygen is typically replaced with nitrogen, commonly known as an inert gas, or carbon dioxide, which can lower the pH or inhibit the growth of bacteria.
In the context of food products, modified atmosphere packaging is generally considered a technique used for prolonging the shelf-life of fresh or minimally processed foods. In this preservation technique, the air surrounding the food in the package is changed to another composition using, for example, a gas-flush process. The initial fresh state of the food may be prolonged by slowing the natural deterioration of the food product. Respiring foods such as fruits and vegetables continue to take in oxygen and give off carbon dioxide as they continue to respire and ripen after harvest. Refrigeration and controlled atmosphere storage methods may be used to retard the ripening process. Reducing temperature slows the produce metabolism, including the rate of respiration. Under controlled atmosphere storage, respiration and ripening may be reduced further by lowering the oxygen content of the air, which normally consists of approximately 21% oxygen, 78% nitrogen, and 1% other elements.
A recent need for using modified atmospheres, specifically carbon dioxide (CO2), is to enhance the flavor of foods by creating an effervescent character during tasting (e.g. U.S. Pat. No. 5,968,573, which is incorporated herein by reference). This method involves the generation of positive CO2 pressure within a sealable container filled with food such that the CO2 diffuses by osmosis into the water content of the food. The development of carbonated foods (e.g. Fizzy Fruit™) has created a need for a safe and convenient package to distribute single servings.
One example of a package directed to retaining a positive pressure atmosphere within the package is a tennis ball can (or tennis ball tube). The air pressure inside a tennis ball is typically 12 psi (pounds per square inch) greater than the ambient air pressure at sea level. Over time, air escapes from the inside of the ball causing a decrease in the amount of air pushing on the inside of the ball and, consequently, decreasing the bounce characteristics of the ball. To prevent the ball from becoming “flat,” the ball is packaged in a positive pressure tube, with the tube pressurized to around 12 psi, which is enough to prevent air from escaping from the inside of the ball. Another example of a positive pressure package is the ubiquitous soda bottle, which is directed to maintaining carbon dioxide saturated liquid under pressures of up to 50 psi.
Designs for a high pressure food package and system that provides a sufficiently pressurized and controllable gaseous environment are needed. Such designs need to be applicable for use with the carbonated fruits or vegetables products described in U.S. Pat. Nos. 5,968,573 and 7,228,793, and U.S. patent application Ser. Nos. 10/857,043, 11/453,712, 11/454,814, 11/548,212, 11/943,964, and 12/271,797, all commonly owned or licensed by The Fizzy Fruit Company and each of which is incorporated herein by reference.